com.google.javascript.jscomp.ReplacedStringsDecoder.java Source code

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Here is the source code for com.google.javascript.jscomp.ReplacedStringsDecoder.java

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/*
 * Copyright 2016 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.javascript.jscomp;

import com.google.common.collect.ImmutableMap;
import com.google.errorprone.annotations.Immutable;

/**
 * A decoder for strings encoded by the ReplaceStrings JS compiler pass. This class is immutable.
 *
 */
@Immutable
public final class ReplacedStringsDecoder {

    // The default place holder for replaced string arguments.
    // Note: We're not allowing this to be changed here because it's present in
    // the replacement strings in the js_storage protocol buffer.
    public static final String ARGUMENT_PLACE_HOLDER = "`";

    private final ImmutableMap<String, String> originalToNewNameMap;

    /** A null decoder that does no mapping. */
    public static final ReplacedStringsDecoder NULL_DECODER = new ReplacedStringsDecoder(
            VariableMap.fromMap(ImmutableMap.<String, String>of()));

    public ReplacedStringsDecoder(VariableMap variableMap) {
        // VariableMap is not an immutable type, so we extract the map instead of directly using it.
        this.originalToNewNameMap = ImmutableMap.copyOf(variableMap.getOriginalNameToNewNameMap());
    }

    /**
     * Decodes an encoded string from the JS Compiler ReplaceStrings pass.
     *
     * <p>An original string with args might look like this:
     * <pre>  Error('Some ' + arg1 + ' error ' + arg2 + ' message.');</pre>
     * Which gets replaced with:
     * <pre>  Error('key' + '`' + arg1 + '`' + arg2);</pre>
     * Where ` is the argument place holder. The replacement mapping would be:
     * <pre>  key  'Some ` error ` message.'</pre>
     * Where key is some arbitrary replacement string. An encoded string,
     * with args, from the client will look like:
     * <pre>  'key`arg1`arg2'</pre>
     *
     * @param encodedStr An encoded string.
     * @return The decoded string, or the encoded string if it fails to decode.
     * @see com.google.javascript.jscomp.ReplaceStrings
     */
    public String decode(String encodedStr) {
        String[] suppliedBits = encodedStr.split(ARGUMENT_PLACE_HOLDER, -1);
        String originalStr = originalToNewNameMap.get(suppliedBits[0]);
        if (originalStr == null) {
            return encodedStr; // Failed to decode.
        }
        String[] originalBits = originalStr.split(ARGUMENT_PLACE_HOLDER, -1);
        StringBuilder sb = new StringBuilder(originalBits[0]);
        for (int i = 1; i < Math.max(originalBits.length, suppliedBits.length); i++) {
            // Replace missing bits with "-". Shouldn't happen except that we aren't
            // escaping the replacement token at the moment.
            sb.append(i < suppliedBits.length ? suppliedBits[i] : "-");
            sb.append(i < originalBits.length ? originalBits[i] : "-");
        }
        return sb.toString();
    }

}